Partial or incomplete combustion of hydrocarbon fuels results in atmospheric pollutants, such as soot, as well as carbon monoxide, and other gases considered toxic and mutagenic, such as the nitrogen oxides. The carbon-containing fuels form soot during the combustion process and are released as emissions, which are harmful to the environment and the health and safety of living beings.
A wide variety of approaches have focused on reducing the emission of such condensed particles, hereinafter designated as “soot,” whether carbon-based or other type of condensed material. One approach has been to develop a comprehensive emission control system involving the combustion and fuel injection process, the fuel composition, and the overall control strategy for the combined operation of the engine that inhibits the formation of unacceptable emission products. Another approach has been to develop devices, such as catalytic converters, particulate traps, filters and systems that treat exhaust products after their formation. Thus, the challenge is viewed as preventing the formation of soot or collecting and destroying soot after it has formed.
With regard to the use of additives or materials, including rare earth metal oxides and particularly ceria (cerium oxide), in emission control systems, U.S. Pat. No. 6,093,223 to Lemaire et al. discloses burning a combustible material or fuel after the addition of a concentrated solution of cerium compounds in ranges of from 50 to 150 parts per million (ppm) to reduce the formation of soot, or alternatively, producing aggregates of ceric oxide by burning a hydrocarbon fuel in the presence of a seed amount of ceric oxide crystallites.
U.S. Pat. No. 6,680,279 B2 to Cai et al. discloses a method of dispersing nanosized catalyst particles on the surface of larger catalyst carrier particles, which include cerium oxide mixed with alumina to increase oxygen storage capacity, for automotive exhaust gas treatment or for a fuel cell reformer. U.S. Pat. No. 6,660,683 B1 to Yaluris et al. describes a particulate composition comprising acidic metal oxide, alkaline earth metal, an oxygen storage component, such as cerium oxide, and a noble metal component for the reduction of nitrous oxides in refinery processes. U.S. Pat. No. 6,588,204 B2 to Hirota et al. describes a particulate filter in an exhaust system wherein a noble metal catalyst and an active oxygen-releasing agent (such as ceria) are used to oxidize and remove the particulates trapped in the filter. There is also a method for treating the atmosphere to remove pollutants as disclosed in U.S. Pat. No. 6,616,903 B2 to Poles et al. Poles et al. equips billboards, solar panels or similar outdoor devices with catalysts on ceria support to convert pollutants to non-objectionable materials or adsorption compositions to collect pollutants for later destruction.
However, the above-mentioned references use ceria crystallites, aggregates, particles and nanoparticles of a different size and oxygen storage capability than the ceria nanoparticles of the present invention. The ceria nanoparticles disclosed herein have been engineered for use in a liquid, gaseous or solid fuel and prevent the formation of soot or other objectionable pollutants during combustion.
Governmental concern for the harmful effects of soot on the environment, including the health and safety of all life forms, leads to worldwide regulations enacted to reduce both particulate matter (soot) and nitrogen oxides. In the United States alone, there are regulatory measures mandating a 98.3% reduction in 1990 allowable levels for particulate emissions from on-road vehicles by the year 2007. Smog and particulate matter account for 15,000 premature deaths and 400,000 asthma attacks annually in the US.
There is a need to identify the best technology to address emissions reduction, engine efficiency and fuel consumption issues. None of the prior art methods, processes, and devices is deemed satisfactory. Prior methods have difficulty when combining the emissions-reducing additive with the fuel due to incompatibility and settling issues.